This invention relates to a chemical reactor. More particularly, this invention relates to a plate-type chemical reactor for reacting two or more fluid components, wherein the reactor contains both static mixing means and heat exchange means.
Chemical reactors are widely used in industry to carry out reactions between two or more fluid components, for example, between liquids and liquids, gases and gases, slurries and slurries, liquids and gases, liquids and slurries, and gases and slurries.
Many industrial reactors are large, fixed-site units designed for continuous operation at roughly constant throughput. These reactors typically have a conventional shell-and-tube design wherein reactants pass through catalyst-containing tubes while heat, usually in the form of hot gases contained within the shell, is applied to the outside of the tube.
A major drawback to shell-and-tube type reactors in general is the size of these reactors. Their large size makes these reactors less desirable for use in applications requiring a more compact reactor. For such applications, plate-and-frame design reactors tend to be preferred.
Plate-and-frame type reactors provide a more compact overall unit than the conventional shell-and-tube reactors and also provide a high degree of modularity. For these reasons, plate-and-frame reactors tend to be used in industrial applications which require high performance and efficiency with relatively low cost, small volume, and light weight.
Plate-and-frame type reactors are disclosed, for example, in U.S. Pat. Nos. 5,209,906 and 4,933,242.
Despite their relatively compact size, however, many plate-and-frame reactors are still undesirably bulky and expensive to make. This is generally because the plates in these reactors tend to be thick. Such thick plates make these plate-type reactors bulky and, therefore, more expensive to make, inspect, clean, re-use and/or replace. It would be desirable, therefore, to provide less bulky plate-type reactors. Less bulky plate-type reactors can be produced more economically and more efficiently on demand with a variety of different interchangeable structures to satisfy a wide variety of needs.
Many reactions carried out in reactors either generate or absorb heat. Such reactions include, for example, those involving the processing of viscous liquids or the reaction of gaseous or liquid systems in contact with a solid catalyst. In such reactions, it is often vital to maintain the reactants at a closely specified temperature and to remove or add heat during the process depending on whether the reaction is exothermic or endothermic. Inadequate temperature control can lead to undesirable products. For example, in free radical polymerizations, the loss or lack of adequate temperature control can result in products having undesirable molecular weight and, hence, undesirable physical properties. In isothermal reactions, inadequate temperature control may lead to undesired crosslinking, or, where a thermoplastic product is desired, to the formation of undesirable crosslinked gels. In some cases, excessive temperature may cause depolymerization coupled with degradation of the molecular weight.
In many instances, temperature gradients combined with residence time variations can lead to significantly low product yields.
Precise control of reaction conditions can be particularly necessary in reactions carried out in stages. In such reactions, a first stage often requires certain component concentrations, dwell times, and temperatures for optimum results, while subsequent stages require a different set of conditions to most efficiently produce a product having maximum purity.
Therefore, it is desirable to provide a reactor which has means for controlling the temperature and the residence time of the reactants therein, whether the reaction is carried out in a single stage or in multiple stages. Reactors which reportedly have means for controlling temperature are disclosed, for example, in U.S. Pat. No. 5,209,906 to Watkins et al.; U.S. Pat. No. 4,421,162 to Tollar; and U.S. Pat. No. 3,528,783 to Haseldon, all of which are hereby incorporated by reference herein.
It is further desirable that a reactor have means therein for mixing the reactants.
Mixers generally fall into two classes, i.e., continuous mixers and batch mixers. In a continuous mixer, components to be mixed are introduced at a particular flow rate into a mixing chamber where the components are mixed by means of mechanical stirring and/or the action of the velocity and turbulence of the components. Unfortunately, continuous mixers do not always provide sufficient contact between molecules of the components to effect complete mixing thereof. If the object of the mixing is to react the components, excess reagent is often required to compensate for the inefficiency of the mixing and to achieve as much contact between the molecules of the components as possible. Thus, the inefficiency of continuous mixers results in additional costs associated with the use of excess reagent as well as the use of energy to operate the mixer.
In a batch mixer, a plurality of components to be mixed are placed in a container and mixed together by means of stirring, rotation, tumbling or the like. Batch mixers also have drawbacks. For example, batch mixing is relatively slow since the process involves feeding the components into the mixing chamber, mixing the components for a period of time sufficient to mix the entire volume of components, and then removing the mixture from the mixing chamber. In addition, batch mixers are typically large structures since an entire batch is mixed at one time. Furthermore, batch mixers tend to operate inefficiently.
It is desirable, therefore, to provide a reactor which itself contains a mixing means so as to efficiently and thoroughly mix together a plurality of components. It is further desirable that such a mixing means be completely static in operation and include no moving parts. In addition, it is desirable that such a mixing means be flexible enough to accommodate a variety of specific needs and system configurations. Furthermore, it is desirable that the reactor provide temperature control at the region therein where mixing takes place.
Static mixers are well known mixing devices which generally contain no moving parts. Mixing is achieved in static mixers by directing a moving stream against stationary elements which twist and cut the stream or force the stream through channels or tubes. The multiple subdividing and recombining of a stream in the static mixer homogenizes the stream. Static mixers may also be used to mix together two diverse fluids or to blend together various components broken down from a single fluid. For example, raw milk containing large globules of butter fat is frequently homogenized into a uniform and consistent product by means of a static mixer.
It is desirable, therefore, that the mixing means in the reactor be composed of a static mixer.
A primary object of the present invention is to provide a reactor containing means therein for controlling temperature of the components to be reacted.
Another object of the present invention is to provide a reactor containing means therein for mixing the components.
A further object of the present invention is to provide a reactor which is capable of mixing components therein at a point where temperature is best controlled.
A further object of the present invention is to provide a reactor containing means therein for controlling temperature in said mixing means.
Another object of this invention is to provide a reactor having means for controlling the degree of mixing of the components.
A still further object of the present invention is to provide a reactor having means therein for controlling the residence time of the components in the reactor.
Another object of this invention is to provide a reactor having means for controlling the degree of mixing of the components.
An additional object of this invention is to provide a reactor having means for controlling residence time of the components, temperature of the components, and degree of mixing in stages.
Another object of the present invention is to provide a reactor which is less bulky and less expensive to make, clean, inspect, re-use and replace than prior reactors.
A still further object of this invention is to provide a method of reacting two or more components by means of a reactor having the characteristics set forth in one or more of the foregoing objects.
These and other objects which are achieved according to the present invention can be discerned from the following description.